As the old saying goes, there’s more than one way to skin a cat. However, when you discover the most efficient and cost-effective way, you tend to stick with that way. Such is the case with the electric motor manufacturer Baldor Electric, based in Fort Smith, Arkansas.
When broaching internal keyways, everyone has their favorite method—vertical slotting, wobble or rotary broaching or push or pull broaching. However, the engineers at this Baldor plant are going with a different method.
“We’ve tried every way you can think of to broach these internal keyways, but what we’ve found is the most efficient, and that is to broach on a CNC lathe with a locking spindle,” says Tom Studie, Baldor machine operator for 31 years.
“Sometime last year, our engineer approached me about using a different tool and insert to broach on the same Okuma Cadet CNC. The new tool he gave me didn’t have a brazed insert like I was used to seeing. Instead, it had a removable, indexable, TiN-coated micro-grain carbide insert, held in by two small set screws,” Mr. Studie adds.
The tool Mr. Studie tested was an indexable inserted broaching tool from Razorform Tools. With this tool, it’s not necessary to take the broaching tool out of the machine to change the insert. Instead, the insert is fastened with screws, making it easy for inserts to be turned around.
“We went from cutting 20 to 30 parts of 4140 steel per brazed insert and sending the tool back to get re-sharpened, to cutting more than 100 parts per cutting edge and indexing the insert when it dulls,” Mr. Studie explains. “The tool stays in the machine while you change out the insert, saving 10 to 15 minutes of having to re-zero the machine.”
The inserts’ design is said to make them last longer than other inserted broaching tools. The combination of relief angles support greater longitudinal force, therefore, reducing breakdowns at the cutting edge. Also, the broaching toolholder geometry is said to offer more stability. Operators comment that the only way the tools break is if the operator crashes them. This greater stability in the holder translates to more support for the insert and less chatter.
Because the company was cutting eight times as many parts per insert and saving 10 to 15 minutes of setup each time an insert edge dulls, it wasn’t long before the Fort Smith plant was broaching exclusively with Razorform tools. Tools and inserts currently being used at the Fort Smith Baldor plant are 0.127" (1/8" keyway), 0.158" (5/32"), 0.190" (3/16"), 0.199" (25/128"), 0.239" (15/64"), 0.252" (1/4"), and 0.318" (5/16"), with larger sizes and variations being developed for cost savings at other Baldor plants.
Broaching on a CNC lathe has saved the company downtime, making this the most efficient way for the company to reach its goal of broaching internal keyways.